(1) Field of the Invention
The present invention relates to a rotor provided with a device for protecting it against lightning, and to an aircraft provided with said rotor, such as a rotary-wing aircraft.
The invention thus lies in the technical field of means for providing protection against lightning, and more particularly means for providing rotary-wing aircraft with protection against lightning.
(2) Description of Related Art
Aircraft are likely to be struck by lightning while flying in difficult weather conditions. In the event of a lightning strike, it is appropriate to verify that the aircraft has not been damaged. Unfortunately, it is particularly difficult to detect the path followed by the lightning after such a strike, and consequently to detect which mechanical and electrical pieces of equipment have conveyed a potentially destructive electric current.
On a helicopter provided with a rotary wing having a main lift rotor driven by a power gearbox, lightning generally strikes the main rotor, and passes through the helicopter airframe, prior to escaping from the helicopter, e.g. via its tail. By way of example, there may be damage to the power gearbox, and in particular its epicyclic speed reduction stage, to the means fastening the gearbox to the airframe, or indeed to the electronic equipment through which the lightning has passed.
Nevertheless, since it is difficult to identify the path followed by the lightning, a lightning strike may lead to the helicopter being grounded for a long time while the manufacturer verifies proper operation of a large number of items of equipment. Under extreme circumstances, such a strike may lead to all of the equipment that might have been affected being replaced.
In particular, the teaching of the following documents is known: U.S. Pat. No. 7,377,750 B1; EP 1 154 537 A2; EP 1 930 586 A1; EP 0 718 495 A1; EP 0 754 624 A1; and U.S. Pat. No. 4,625,256 A.
Furthermore, document US 2009/038819 presents a wind turbine provided with a nacelle carried by a mast, the nacelle supporting a rotor that rotates about a horizontal axis of rotation.
The wind turbine is provided with rotary protection means and stationary protection means connected together by connection means provided with two contact means, those contact means being connected together by an electrical conductor that establishes a continuous connection.
Document U.S. Pat. No. 4,625,256 describes a wind turbine having a rotor fastened on a drive shaft that extends along a vertical axis of rotation.
Furthermore, the wind turbine possesses protection means for defining a privileged path to be followed by an electric current generated by a lightning strike. Those protection means comprise a rotary first ring of frustoconical shape fastened to the drive shaft and a non-rotary second ring also of frustoconical shape, the first and second rings being separated by an annular space.